I'm new to using Java, but I have some previous experience with C#. The issue I'm having comes with reading user input from console.
I'm running into the "java.util.NoSuchElementException" error with this portion of code:
payment = sc.next(); // PromptCustomerPayment function
I have two functions that get user input:
If I don't call PromptCustomerQty then I don't get this error, which leads me to believe I am doing something wrong with scanner. Below is my full code sample. I appreciate any help.
public static void main (String[] args) {
// Create a customer
// Future proofing the possabiltiies of multiple customers
Customer customer = new Customer("Will");
// Create object for each Product
// (Name,Code,Description,Price)
// Initalize Qty at 0
Product Computer = new Product("Computer","PC1003","Basic Computer",399.99);
Product Monitor = new Product("Monitor","MN1003","LCD Monitor",99.99);
Product Printer = new Product("Printer","PR1003x","Inkjet Printer",54.23);
// Define internal variables
// ## DONT CHANGE
ArrayList<Product> ProductList = new ArrayList<Product>(); // List to store Products
String formatString = "%-15s %-10s %-20s %-10s %-10s %n"; // Default format for output
// Add objects to list
ProductList.add(Computer);
ProductList.add(Monitor);
ProductList.add(Printer);
// Ask users for quantities
PromptCustomerQty(customer, ProductList);
// Ask user for payment method
PromptCustomerPayment(customer);
// Create the header
PrintHeader(customer, formatString);
// Create Body
PrintBody(ProductList, formatString);
}
public static void PromptCustomerQty(Customer customer, ArrayList<Product> ProductList) {
// Initiate a Scanner
Scanner scan = new Scanner(System.in);
// **** VARIABLES ****
int qty = 0;
// Greet Customer
System.out.println("Hello " + customer.getName());
// Loop through each item and ask for qty desired
for (Product p : ProductList) {
do {
// Ask user for qty
System.out.println("How many would you like for product: " + p.name);
System.out.print("> ");
// Get input and set qty for the object
qty = scan.nextInt();
}
while (qty < 0); // Validation
p.setQty(qty); // Set qty for object
qty = 0; // Reset count
}
// Cleanup
scan.close();
}
public static void PromptCustomerPayment (Customer customer) {
// Initiate Scanner
Scanner sc = new Scanner(System.in);
// Variables
String payment = "";
// Prompt User
do {
System.out.println("Would you like to pay in full? [Yes/No]");
System.out.print("> ");
payment = sc.next();
} while ((!payment.toLowerCase().equals("yes")) && (!payment.toLowerCase().equals("no")));
// Check/set result
if (payment.toLowerCase() == "yes") {
customer.setPaidInFull(true);
}
else {
customer.setPaidInFull(false);
}
// Cleanup
sc.close();
}
This question is related to
java
input
java.util.scanner
The problem is
When a Scanner is closed, it will close its input source if the source implements the Closeable interface.
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Scanner.html
Thus scan.close()
closes System.in
.
To fix it you can make
Scanner scan
static
and do not close it in PromptCustomerQty. Code below works.
public static void main (String[] args) {
// Create a customer
// Future proofing the possabiltiies of multiple customers
Customer customer = new Customer("Will");
// Create object for each Product
// (Name,Code,Description,Price)
// Initalize Qty at 0
Product Computer = new Product("Computer","PC1003","Basic Computer",399.99);
Product Monitor = new Product("Monitor","MN1003","LCD Monitor",99.99);
Product Printer = new Product("Printer","PR1003x","Inkjet Printer",54.23);
// Define internal variables
// ## DONT CHANGE
ArrayList<Product> ProductList = new ArrayList<Product>(); // List to store Products
String formatString = "%-15s %-10s %-20s %-10s %-10s %n"; // Default format for output
// Add objects to list
ProductList.add(Computer);
ProductList.add(Monitor);
ProductList.add(Printer);
// Ask users for quantities
PromptCustomerQty(customer, ProductList);
// Ask user for payment method
PromptCustomerPayment(customer);
// Create the header
PrintHeader(customer, formatString);
// Create Body
PrintBody(ProductList, formatString);
}
static Scanner scan;
public static void PromptCustomerQty(Customer customer, ArrayList<Product> ProductList) {
// Initiate a Scanner
scan = new Scanner(System.in);
// **** VARIABLES ****
int qty = 0;
// Greet Customer
System.out.println("Hello " + customer.getName());
// Loop through each item and ask for qty desired
for (Product p : ProductList) {
do {
// Ask user for qty
System.out.println("How many would you like for product: " + p.name);
System.out.print("> ");
// Get input and set qty for the object
qty = scan.nextInt();
}
while (qty < 0); // Validation
p.setQty(qty); // Set qty for object
qty = 0; // Reset count
}
// Cleanup
}
public static void PromptCustomerPayment (Customer customer) {
// Variables
String payment = "";
// Prompt User
do {
System.out.println("Would you like to pay in full? [Yes/No]");
System.out.print("> ");
payment = scan.next();
} while ((!payment.toLowerCase().equals("yes")) && (!payment.toLowerCase().equals("no")));
// Check/set result
if (payment.toLowerCase() == "yes") {
customer.setPaidInFull(true);
}
else {
customer.setPaidInFull(false);
}
}
On a side note, you shouldn't use ==
for String comparision, use .equals
instead.
You need to remove the scanner closing lines: scan.close();
It happened to me before and that was the reason.
the reason of the exception has been explained already, however the suggested solution isn't really the best.
You should create a class that keeps a Scanner as private using Singleton Pattern, that makes that scanner unique on your code.
Then you can implement the methods you need or you can create a getScanner ( not recommended ) and you can control it with a private boolean, something like alreadyClosed.
If you are not aware how to use Singleton Pattern, here's a example:
public class Reader {
private Scanner reader;
private static Reader singleton = null;
private boolean alreadyClosed;
private Reader() {
alreadyClosed = false;
reader = new Scanner(System.in);
}
public static Reader getInstance() {
if(singleton == null) {
singleton = new Reader();
}
return singleton;
}
public int nextInt() throws AlreadyClosedException {
if(!alreadyClosed) {
return reader.nextInt();
}
throw new AlreadyClosedException(); //Custom exception
}
public double nextDouble() throws AlreadyClosedException {
if(!alreadyClosed) {
return reader.nextDouble();
}
throw new AlreadyClosedException();
}
public String nextLine() throws AlreadyClosedException {
if(!alreadyClosed) {
return reader.nextLine();
}
throw new AlreadyClosedException();
}
public void close() {
alreadyClosed = true;
reader.close();
}
}
Source: Stackoverflow.com